The present invention relates to an improvement in the process for the preparation of carboxylic acids prepared by the reaction of ethylenically unsaturated compounds with carbon monoxide and water in the presence of catalyst compositions comprising rhodium or iridium compounnds and a halogen promoter. More particularly, the invention relates to increasing the rate of reaction in such a process by employing certain compounds as additives in the reaction.
The preparation of carboxylic acids and ester derivatives thereof from olefins and other ethylenically unsaturated compounds, carbon monoxide and water is well known in the art. A number of catalysts have been disclosed for the reaction at elevated temperatures and pressures. More recently, a process has been developed which employs more reactive and more stable catalysts whereby lower temperatures and pressures can be employed in the process resulting in a higher yield of the desired carboxylic acid with no substantial formation of undesirable by-products. These catalysts generally contain two components, namely, a rhodium or iridum compound and a halogen component. The catalysts and the process in which they are employed are described in detail in U.S. Pat. Nos. 3,579,552 and 3,579,551. While this process is, in general, satisfactory for commercial operation, it has now been discovered that production of acid per unit time can be substantially increased by carrying out the reaction in the presence of certain compounds which accelerate the rate of reaction, hereinafter referred to simply as "accelerators."